1. Field of the Invention
The present invention relates to an oil cooler for a vehicle, in which a heat exchange core is housed in a casing such that a cooling water passage is formed around the heat exchange core, wherein the casing includes a cylindrical sidewall part, the heat exchange core includes an inlet-side oil passage and an outlet-side oil passage which extend parallel to each other along an axis of the sidewall part, the heat exchange core enables oil to be delivered from the inlet-side oil passage to the outlet-side oil passage, and an inlet pipe and an outlet pipe are connected to the sidewall part, the inlet pipe forming a cooling water inlet passage in communication with the cooling water passage, and the outlet pipe forming a cooling water outlet passage in communication with the cooling water passage.
2. Description of the Related Art
Japanese Patent Application Laid-open No. 2001-215091 has made known the following oil cooler for a vehicle. In the oil cooler, a heat exchange core is housed in a cylindrical casing with first and second plates fastened to its opposite end portions, and the heat exchange core includes an inlet-side oil passage and an outlet-side oil passage which extend parallel to each other along the axis of the casing. An inlet pipe and an outlet pipe are connected to the casing. The inlet pipe forms a cooling water inlet passage, and the outlet pipe forms a cooling water outlet passage.
In the conventional oil cooler as disclosed by Japanese Patent Application Laid-open No. 2001-215091, a spacing between the outer periphery of the heat exchange core and the inner periphery of the casing is narrow, and the flow of cooling water in such a narrow spacing increases the flow rate of the cooling water locally. For this reason, it is likely that cavitation may occur near the inlet-side oil passage where the temperature of the flowing oil is higher than any other part, and that erosion may occur. Measures for preventing such troubles include: enlarging the spacing between the outer periphery of the heat exchange core and the inner periphery of the casing; and arranging the inlet-side oil passage such that it is spaced away from the inner surface of the casing. However, if the spacing is increased, the outer peripheral radius of the heat exchange core has to be decreased, and the heat exchange efficiency accordingly deteriorates. On the other hand, if the inner peripheral radius of the casing is increased, the oil cooler has to be constructed in a larger size. Moreover, if the inlet-side oil passage is arranged spaced away from the inner surface of the casing, the distance between the inlet-side oil passage and the outlet-side oil passage is shortened, and the heat exchange efficiency accordingly deteriorates.